Grass clippings under a mower deck hold moisture and can interfere with airflow. Cleaning them safely starts with disconnecting the spark plug or removing the battery and keeping hands away from the blade.
Make the mower safe
Switch off the engine, remove the key if present, disconnect the spark-plug wire or battery, and wait for every moving part to stop. Wear gloves and eye protection.
Brush instead of reaching
Tip the mower only as the manual permits, keeping the air filter and fuel system oriented correctly. Use a stiff brush or plastic scraper rather than your hands or a metal tool near the blade.
Inspect before storage
Look for a bent blade, damaged guard, blocked discharge chute, or loose fastener. Let the deck dry before reconnecting power, then test briefly in an open area.
Cleaning after damp mowing prevents buildup and makes the next inspection easier.